﻿using System;
using System.IO;
using System.IO.Compression;
using static QRCoder.QRCodeGenerator;

namespace QRCoder
{
    public sealed class PngByteQRCode : AbstractQRCode, IDisposable
    {
        /// <summary>
        /// Constructor without params to be used in COM Objects connections
        /// </summary>
        public PngByteQRCode() { }

        public PngByteQRCode(QRCodeData data) : base(data)
        {
        }


        /// <summary>
        /// Creates a black &amp; white PNG of the QR code, using 1-bit grayscale.
        /// </summary>
        public byte[] GetGraphic(int pixelsPerModule)
        {
            using (var png = new PngBuilder())
            {
                var size = this.QrCodeData.ModuleMatrix.Count * pixelsPerModule;
                png.WriteHeader(size, size, 1, PngBuilder.ColorType.Greyscale);
                png.WriteScanlines(this.DrawScanlines(pixelsPerModule));
                png.WriteEnd();
                return png.GetBytes();
            }
        }

        /// <summary>
        /// Creates 2-color PNG of the QR code, using 1-bit indexed color. Accepts 3-byte RGB colors for normal images and 4-byte RGBA-colors for transparent images.
        /// </summary>
        public byte[] GetGraphic(int pixelsPerModule, byte[] darkColorRgba, byte[] lightColorRgba)
        {
            using (var png = new PngBuilder())
            {
                var size = this.QrCodeData.ModuleMatrix.Count * pixelsPerModule;
                png.WriteHeader(size, size, 1, PngBuilder.ColorType.Indexed);
                png.WritePalette(darkColorRgba, lightColorRgba);
                png.WriteScanlines(this.DrawScanlines(pixelsPerModule));
                png.WriteEnd();
                return png.GetBytes();
            }
        }

        /// <summary>
        /// Creates a bitmap where each pixel is represented by a single bit, dark = 0 and light = 1.
        /// </summary>
        private byte[] DrawScanlines(int pixelsPerModule)
        {
            var moduleMatrix = this.QrCodeData.ModuleMatrix;
            var matrixSize = moduleMatrix.Count;
            var bytesPerScanline = (matrixSize * pixelsPerModule + 7) / 8 + 1; // A monochrome scanline is one byte for filter type then one bit per pixel.
            var scanlines = new byte[bytesPerScanline * matrixSize * pixelsPerModule];

            for (var y = 0; y < matrixSize; y++)
            {
                var modules = moduleMatrix[y];
                var scanlineOffset = y * pixelsPerModule * bytesPerScanline;

                // Draw a scanline with the modules from the QR code.
                for (var x = 0; x < matrixSize; x++)
                {
                    if (modules[x])
                    {
                        continue;
                    }

                    var pixelIndex = x * pixelsPerModule;
                    var endIndex = pixelIndex + pixelsPerModule;
                    for (; pixelIndex < endIndex; pixelIndex++)
                    {
                        scanlines[scanlineOffset + 1 + pixelIndex / 8] |= (byte)(0x80 >> (pixelIndex % 8));
                    }
                }

                // Copy the scanline required number of times.
                for (var copyCount = 1; copyCount < pixelsPerModule; copyCount++)
                {
                    Array.Copy(scanlines, scanlineOffset, scanlines, scanlineOffset + copyCount * bytesPerScanline, bytesPerScanline);
                }
            }

            return scanlines;
        }

        /// <summary>
        /// Writes the chunks that make up a PNG file.
        /// </summary>
        /// <remarks>
        /// See https://www.w3.org/TR/2003/REC-PNG-20031110 and https://www.ietf.org/rfc/rfc1950.txt.
        /// </remarks>
        private sealed class PngBuilder : IDisposable
        {
            private static readonly byte[] PngSignature = { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A };

            private static readonly uint[] CrcTable = {
                0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B, 0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924, 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
                0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01, 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F, 0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
                0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5, 0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236, 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
                0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713, 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9, 0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
            };

            // ReSharper disable InconsistentNaming
            // Chunk types
            private static readonly byte[] IHDR = { 73, 72, 68, 82 };

            private static readonly byte[] IDAT = { 73, 68, 65, 84 };

            private static readonly byte[] IEND = { 73, 69, 78, 68 };

            private static readonly byte[] PLTE = { 80, 76, 84, 69 };

            private static readonly byte[] tRNS = { 116, 82, 78, 83 };
            // ReSharper enable InconsistentNaming

            public enum ColorType : byte
            {
                Greyscale = 0,
                Indexed = 3
            }

            private MemoryStream stream = new MemoryStream();

            public void Dispose()
            {
                this.stream?.Dispose();
                this.stream = null;
            }

            public byte[] GetBytes()
            {
                var bytes = this.stream.ToArray();

                // Enumerate chunks in file and insert their CRC32 checksums.
                var chunkOffset = PngSignature.Length;
                while (chunkOffset < bytes.Length)
                {
                    // Read length field.
                    var dataLength = (bytes[chunkOffset] << 24) | (bytes[chunkOffset + 1] << 16) | (bytes[chunkOffset + 2] << 8) | bytes[chunkOffset + 3];

                    // CRC is computed from type and data fields.
                    var crc = Crc32(bytes, chunkOffset + 4, dataLength + 4);

                    // Write CRC to end of chunk.
                    var crcOffset = chunkOffset + 8 + dataLength;
                    bytes[crcOffset + 0] = (byte)(crc >> 24);
                    bytes[crcOffset + 1] = (byte)(crc >> 16);
                    bytes[crcOffset + 2] = (byte)(crc >> 8);
                    bytes[crcOffset + 3] = (byte)crc;

                    // Seek to next chunk.
                    chunkOffset = crcOffset + 4;
                }

                return bytes;
            }

            /// <summary>
            /// Writes the IHDR chunk. This must be the first chunk in the file.
            /// </summary>
            public void WriteHeader(int width, int height, byte bitDepth, ColorType colorType)
            {
                this.stream.Write(PngSignature, 0, PngSignature.Length);
                this.WriteChunkStart(IHDR, 13);

                // Size.
                this.WriteIntBigEndian((uint)width);
                this.WriteIntBigEndian((uint)height);

                // Color.
                this.stream.WriteByte(bitDepth);
                this.stream.WriteByte((byte)colorType);

                // Constants.
                this.stream.WriteByte(0);
                this.stream.WriteByte(0);
                this.stream.WriteByte(0);

                this.WriteChunkEnd();
            }

            /// <summary>
            /// Writes the PLTE chunk, and also the tRNS chunk if necessary. Must come before the IDAT chunk.
            /// </summary>
            public void WritePalette(params byte[][] rgbaColors)
            {
                const int Red = 0, Green = 1, Blue = 2, Alpha = 3;
                const byte Opaque = 255;
                var hasAlpha = false;

                this.WriteChunkStart(PLTE, 3 * rgbaColors.Length);
                foreach (var color in rgbaColors)
                {
                    hasAlpha |= color.Length > Alpha && color[Alpha] < Opaque;
                    this.stream.WriteByte(color[Red]);
                    this.stream.WriteByte(color[Green]);
                    this.stream.WriteByte(color[Blue]);
                }
                this.WriteChunkEnd();

                if (!hasAlpha)
                {
                    return;
                }

                this.WriteChunkStart(tRNS, rgbaColors.Length);
                foreach (var color in rgbaColors)
                {
                    this.stream.WriteByte(color.Length > Alpha ? color[Alpha] : Opaque);
                }
                this.WriteChunkEnd();
            }

            /// <summary>
            /// Writes the IDAT chunk with the actual picture.
            /// </summary>
            public void WriteScanlines(byte[] scanlines)
            {
                using (var idatStream = new MemoryStream())
                {
                    Deflate(idatStream, scanlines);

                    this.WriteChunkStart(IDAT, (int)(idatStream.Length + 6));

                    // Deflate header.
                    this.stream.WriteByte(0x78); // 8 Deflate algorithm, 7 max window size
                    this.stream.WriteByte(0x9C); // Check bits.

                    // Compressed data.
                    idatStream.Position = 0;
#if NET35
                    idatStream.WriteTo(this.stream);
#else
                    idatStream.CopyTo(this.stream);
#endif
                    // Deflate checksum.
                    var adler = Adler32(scanlines, 0, scanlines.Length);
                    this.WriteIntBigEndian(adler);

                    this.WriteChunkEnd();
                }
            }

            /// <summary>
            /// Writes the IEND chunk. This must be the last chunk in the file.
            /// </summary>
            public void WriteEnd()
            {
                this.WriteChunkStart(IEND, 0);
                this.WriteChunkEnd();
            }

            private void WriteChunkStart(byte[] type, int length)
            {
                this.WriteIntBigEndian((uint)length);
                this.stream.Write(type, 0, 4);
            }

            private void WriteChunkEnd()
            {
                // Reserves 4 bytes space for crc32 so GetBytes can add it later.
                this.stream.SetLength(this.stream.Length + 4);
                this.stream.Position += 4;
            }

            private void WriteIntBigEndian(uint value)
            {
                this.stream.WriteByte((byte)(value >> 24));
                this.stream.WriteByte((byte)(value >> 16));
                this.stream.WriteByte((byte)(value >> 8));
                this.stream.WriteByte((byte)value);
            }

            private static void Deflate(Stream output, byte[] bytes)
            {
                using (var deflateStream = new DeflateStream(output, CompressionMode.Compress, leaveOpen: true))
                {
                    deflateStream.Write(bytes, 0, bytes.Length);
                }
            }

            // Reference implementation from RFC 1950. Not optimized.
            private static uint Adler32(byte[] data, int index, int length)
            {
                const uint Base = 65521;
                uint s1 = 1, s2 = 0;

                var end = index + length;
                for (var n = index; n < end; n++)
                {
                    s1 = (s1 + data[n]) % Base;
                    s2 = (s2 + s1) % Base;
                }

                return (s2 << 16) + s1;
            }

            // Reference implementation from REC-PNG-20031110. Not optimized.
            private static uint Crc32(byte[] data, int index, int length)
            {
                var c = 0xffffffff;

                var end = index + length;
                for (var n = index; n < end; n++)
                {
                    c = CrcTable[(c ^ data[n]) & 0xff] ^ (c >> 8);
                }

                return c ^ 0xffffffff;
            }
        }
    }

    public static class PngByteQRCodeHelper
    {
        public static byte[] GetQRCode(string plainText, int pixelsPerModule, byte[] darkColorRgba, byte[] lightColorRgba, ECCLevel eccLevel, bool forceUtf8 = false, bool utf8BOM = false, EciMode eciMode = EciMode.Default, int requestedVersion = -1)
        {
            using (var qrGenerator = new QRCodeGenerator())
            using (var qrCodeData = qrGenerator.CreateQrCode(plainText, eccLevel, forceUtf8, utf8BOM, eciMode, requestedVersion))
            using (var qrCode = new PngByteQRCode(qrCodeData))
                return qrCode.GetGraphic(pixelsPerModule, darkColorRgba, lightColorRgba);
        }
    


        public static byte[] GetQRCode(string txt, QRCodeGenerator.ECCLevel eccLevel, int size)
        {
            using (var qrGen = new QRCodeGenerator())
            using (var qrCode = qrGen.CreateQrCode(txt, eccLevel))
            using (var qrPng = new PngByteQRCode(qrCode))
                return qrPng.GetGraphic(size);
        }
    }    
}
